1. Field of the Invention
The present invention relates to a barrel worm-shaped tool used in the grinding processing that is carried out, to finish, with precision, the tooth face of an internal gear after the heat treatment.
2. Description of the Related Art
In a common gear-production method, a form of gear is firstly shaped from a predetermined material of a gear through a processing of cutting teeth. The gear thus formed is then treated by heat, and, after that, the heated gear is finished (by a grinding processing) to remove the buckles and the like generated by the heat treatment. Various conventional-type tooth-profile grinding methods using tools such as WA grinding wheels and super-abrasive grinding wheels (e.g., diamond grinding wheels and CBN grinding wheels) have been employed for the purpose of finishing efficiently the tooth faces of the gear having been treated by heat. The tools used for this purpose have various shapes corresponding to the shapes of gears to be ground. Some of the examples of such shapes of tools include external-gear shapes, internal-gear shapes, and worm shapes.
Among the various types of gears, internal gears are quite often used in such apparatuses as automotive transmissions. The demand for improvement in precision is ever growing. Under the circumstances, a tooth-profile grinding method for the purpose of the grinding finishing on tooth faces of an internal gear using the barrel worm-shaped tool is disclosed in nonpatent document 1. What is proposed in the nonpatent document 1 is a calculation method for the edge profile of a barrel worm-shaped tool. The calculated edge profile of the tool is the one that fits the final state of the tooth profile of the internal gear that has been through the grinding.
[NONPATENT DOCUMENT 1] Shigeru HOYASHITA, “Barrel Worm-Shaped Tool with Conjugate Cutting-Edge Profile Generated from Tooth Profile of Internal Gear,” Journal of the Japan Society of Mechanical Engineers (Series C), Vol. 62, No, 593, January 1996, pp. 284-290